A crank chopper method (another name, an arm method) is known for folding parallel folded objects along a line perpendicular to a cutting surface by use of a chopper blade.
Recently, several methods have been developed by reducing inertia of the chopper blade so as to increase the machine operating speed and vertically move the chopper blade so as to increase the folding accuracy. For example, as shown in FIG. 6, German Federal Republic Laid-Open Application No. 2247707 discloses a device for driving a folding knife.
In that application, a linearly feeding crank mechanism (a slider crank mechanism) A is utilized incorporating a belt or a chain 1, a wheel 2 on which the belt or the chain is wound, a crank shaft 3 integrally attached to the wheel 2, a crank 4 integrally connected to the crank shaft 3, a connecting rod 5 connected to the crank 4 with a pin, a slider 6 connected to the connecting rod 5 by a pivot, and a linear guide 7. A folded object W on a folding table 9 is inserted between folding rollers 10 by vertically moving downwardly a folding knife 8, which is integrally connected to the slider 6.
However, the slider 6 and the linear guide 7 are necessary for the linearly feeding crank mechanism A. Therefore, the size of the mechanism becomes large, and the durability of the mechanism is reduced due to the a sliding surface of the slider can be coming abraded.